MDB & JSP

Question

I am trying one of the examples:
I have a jar file that has MDB class and then I have war file that has jsp that accesses the queue. And jar file and war file is being pacakged in ear file. So my question is that when I deploy .ear does it run in it's own VM. In this example:
1. A.jsp sends message to calculator bean.
2. calculator bean reads the message, does some calculations and add a record to static member of another class RecordBean
3. A.jsp calls B.jsp to display results. And, B.jsp directly accesses the static member of RecordBean.
So my question is that is all that happening in one VM otherwise B.jsp wouldn't have been able to directly access RecordBean. Why is it like that. Please let me know if you want me to post the example.

Answer 1

A static reference to an object instance might be available to all the other object, or not, depending on the class loader hierarchy.
For classes packaged in the same EAR file, they should have no class loader isolation issues, hence your static references should work fine. But for different EARs or different WARs in different EARs or deployed independently, you might end up with class loading issues (this very often depend on your container and the way it interprets/implements J2EE class loading).
You would definitively benefit from reading about core Java knowledge and J2EE as well.